Safety adapter



Feb. 6, 1968 v w R. A. TAYLOR 3,368,110

SAFETY ADAPTER Filed July 12, 1965 INVENTOR ROBERT A. TAYLOR United States Patent 3,368,110 SAFETY ADAPTER Robert A. Taylor, 6640 Hibiscus Ave. S., St. Petersburg, Fla. 33707 Filed July 12, 1965, Ser. No. 471,368 4 Claims. (Cl. 317-16) ABSTRACT OF THE DISCLOSURE An electrical protective device having input and output terminals, fuses between the terminals and a pair of oppositely poled diodes connected in series across the output terminals.

cessive high current over a relatively long period of time.

This high current provides sufficient heat to melt the normal fuse wires and thus create an open circuit so that the device will not be damaged by the excessive current.

However, such a circuit or adapter is not sufiicient to provide protection against high, short-term surges, which occur for numerous reasons, such as lightning.

Accordingly, it is an object of this invention to provide an electrical circuit which includes means for protecting against high, relatively long currents, and, additionally, to protect against sudden high voltage surges.

It is a further object of this invention to provide a housing which will include the above circuit and which may be adaptable for use with the device to be protected.

These and other objects of the invention will become apparent from the following description when taken in conjunction with the drawings wherein:

FIG. 1 shows the housing of an adapter using the circuit of the present invention;

FIG. 2 is a plan view of the adapter of FIG. 1 with the upper housing removed; and

FIG. 3 is a schematic circuit diagram of the present invention.

While the present invention is illustrated by means of an adapter device which includes the circuit protection parameters provided by this invention it is to be understood that such a circuit may be built directly into any particular appliance at the time of manufacture.

Turning now more specifically to FIG. 1, there is shown an adapter device including an upper housing 11 and a mating lower housing 13 which may be secured together by means such as screw 15.

Extending outwardly from within the housing and at one end thereof are two standard contact prongs 19 and 21. At the other end of the housing, the upper and lower sections are formed so as to provide apertures 23 and 25 through the housing.

As shown in FIG. 2 apertures 23 and 25 are adjacent to a pair of metal connectors 27 and 29. The metal connectors have the normal outwardly extending spring fingers 31 and 33 so as to provide a positive contact with the prongs of a plug (not shown) when they are inserted through the apertures 23 and 25.

For purposes of convenience, the entire lower and upper housings may be molded so as to form the necessary extending wall structures, such as at 35 and 37, which bear against and hold the metal connectors 27 and 29. Additionally, such wall members provide a firm holding means for the inner sections of the contact prongs 19 and 21.

Each of the prongs 19 and 21 have an extending leg 39 and 41 respectively so as to provide a means for making the required electrical connections.

One set of such connections includes the leads 47 and 49 which connect fuses 43 and 45 between the contact prongs and the metal connectors 27 and 29.

The device as described thus far will provide the standard overcurrent protection and is similar to many such fuses protective devices.

In order to protect the apparatus being used from surges of high voltage, a pair of oppositely poled diodes 51 and 53 are connected across the contact members 27 and 29 by means such as leads 55 and 57. These diodes are connected in series and may be of any of the type of diodes which have the proper reverse conduction characteristics and which have a breakdown voltage equal to or less than the maximum permissible voltage for the apparatus. One example would be p-n junction semiconductor diodes.

The schematic diagram of FIG. 3 illustrates the principle of the protective circuit of the present invention when an excessive voltage surge occurs at the input terminals 19 and 21, and such voltage exceeds the rated breakdown voltage of the diodes 51 and 53. Current passes through the diodes under these conditions and results in a direct short across the fuses 43 and 45 which will accordingly melt the fuse and open the circuit, thus providing the additional protection as described above.

It will be apparent that the protective circuit of this invention is not limited to any particular rated diodes or fuses since the choice of these components will rest with the rating of the appliance to be used. It will also be apparent that the circuit can easily be adapted for a three wire operation as required for many appliances. Accordingly, the above description and accompanying drawings are illustrative only and the scope of the invention is to be limited only by the following claims.

I claim:

1. A protective circuit comprising:

a pair of input terminals,

a pair of output terminals,

a fuse connected between associated input and output terminals, and

a pair of oppositely poled diodes connected in series across said output terminals.

2. The circuit of claim 1 wherein said diodes are p-n junction semiconductor diodes.

4. The device of claim 3 wherein said diodes are 19-11 7 OTHER R FERENCES junction semiconductor diodes" Phelps, Electrical Protection For Transistorized' References Cited Equipment, July 1958, pp. 247-249, Bell Laboratories UNITED STATES PATENTS 5 894,705 7/ 1908 Schatmer 317-46 MILTON o. HIRSHFIELD, Primary Examiner. 2,520,956 9/1950 Parker 317-31 X 3,047,773 7/ 1962 Morton. J. D. TRAMMELL, Assistant Examiner.

3,187,224 6/1965 Massena 317-16 

